Stats: time period of "Most active" numbers

In the new Dashboard, things are different from what is described in the FAQ screencast about stats. My question was not answered by the screencast.

I'd like to know, with regard to the "Most Active" posts stats, what time period is covered? hard to evaluate the numbers without knowing that. The time period is not "TOday" or "Yesterday," nor is it total since the post went up.
Thanks,
nosleepingdog